In an industrial field for manufacturing an IC chip or the like, a chuck device for holding a semiconductor wafer in a predetermined portion of a processing device is widely used in a semiconductor wafer process. The chuck device may be a mechanical chuck device, a vacuum chuck device or an electrostatic chuck device. The electrostatic chuck device is advantageous especially to reliably attract and fix an uneven semiconductor wafer, and also, the electrostatic chuck device is easy to handle and use even in a vacuum state.
The electrostatic chuck device attracts an object to be attracted such as a wafer or the like by static electricity generated by applying a voltage to an internal electrode embedded in an insulating member. Further, the wafer is processed by, e.g., plasma etching in a state where temperature of the wafer is controlled to be maintained at a desired level by heating an attracting surface (chuck surface) by a heater built in the chuck. A ceramic plate is widely used for an attracting layer forming the wafer attracting surface because of its high resistance to the plasma etching and long life span.
As for the electrostatic chuck device, there is widely used one having a structure in which a metal base and a ceramic plate are adhered to each other by an adhesive. However, in this electrostatic chuck device, an exposed side surface of an adhesive layer between the metal base and the ceramic plate is eroded by the side etching of the plasma during the processing of the wafer. If an outer peripheral portion of the adhesive layer is eroded, thermal conductivity between the ceramic plate and the metal base at the outer peripheral of the ceramic plate becomes different from that at the central portion of the ceramic plate. Therefore, it is difficult to uniformly dissipate heat of the wafer, which is brought to a high temperature by the etching, through the metal base via the ceramic plate and the adhesive layer. This leads to a temperature deviation on the wafer, and desired etching cannot be performed due to the bending of the wafer.
As for the electrostatic chuck device for suppressing erosion of the side surface of the adhesive layer, there is proposed an electrostatic chuck device in which an erosion preventing insulating material is provided at the side surface of the adhesive layer (Japanese Patent Application Publication NO. 2000-114358).
However, the electrostatic chuck device disclosed in Japanese Patent Application Publication NO. 2000-114358 may not sufficiently suppress the erosion of the adhesive layer by the plasma.
When the adhesive layer is eroded, it may be necessary to repair the adhesive layer by applying a liquid adhesive dissolved in a solvent to the eroded portion and performing thermal compression. In this method, however, voids are generated in the repaired portion of the adhesive layer due to evaporation of the solvent. Since the adhesive layer becomes non-uniform, the thermal conductivity of the repaired adhesive layer becomes non-uniform. Accordingly, when the adhesive layer is eroded, the adhesive layer and the ceramic plate are discarded and replaced even if the ceramic plate is still usable.
As described above, when the adhesive layer deteriorates, the ceramic plate has to be replaced regardless of its good durability and long life span and, hence, the characteristics of the ceramic plate cannot be sufficiently utilized. Therefore, it is required to reduce a maintenance cost by preventing replacement of the high-priced ceramic plate while maintaining performance of the electrostatic chuck device by uniformly repairing the eroded side surface of the adhesive layer.